1. Field of the Invention
This application relates to the field of incubators and more particularly to the field of incubators having an external gas feed.
2. Description of Related Art
Incubators are used to cultivate cell cultures. It is desirable to maintain inside the incubator which receives the cell cultures, conditions which are most advantageous for providing optimum cell growth. Particularly important is a constant temperature and a high relative humidity.
Typically, incubators with an external gas feed also maintain in the interior space of the incubator an interior atmosphere with a constant mixing ratio between air and the added gas, which is typically CO.sub.2.O.sub.2 or N.sub.2 may also be added if desired. In order to compensate for disturbances that occur when the incubator with the external gas feed is opened, the gas concentration in the interior space is measured and the gas supply is regulated to maintain a constant gas-to-air mixing ratio.
Conventional incubators with an external gas feed typically include a fan to thoroughly and uniformly mix the added gas with the interior atmosphere. The fan can be implemented in form of a miniature fan, with the drive motor of the fan also arranged in the interior space. Alternatively, only the fan wheel can be placed within the interior space, while the drive motor is located outside the incubator housing. The fan with the drive represents a relatively complex and expensive component. The moving parts of the fan located in the interior space are typically heavy and are also difficult to clean and sterilize, so that the fan itself can pose a contamination risk. If the drive motor is located outside the interior space, then the drive shaft for the fan wheel has to penetrate the wall of the inner vessel of the incubator, which requires an opening and therefore also increases the contamination risk. Moreover, a fan tends to whirl the airborne germs that exist in the interior space, around and spread these germs over the cell cultures.
It is desirable to provide an incubator with an external gas feed that is less complicated and less expensive to build and that also reduces the contamination risk.